Transcript Mackay_2010 - West Virginia University

Ross Mackay, Kentucky Geodetic Adviser
Accessing the
National Spatial Reference System
2010 West Virginia GIS Conference
June 9, 2010
Nothing rocks your world like a geodetic surveyor.
How the States Got Their Shapes, History Channel
following interview with NGS Chief Geodetic Surveyor, Dave Doyle
There’s a Map on My Lap: All About Maps, By Tish Rabe, Illustrated by Aristides Ruiz
National Spatial Reference System
NSRS
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Latitude
Longitude
Height
Gravity
Scale
Orientation
and how these values
change with time
Geodesy layer
Geodetic Datums
Vertical
1-D - Orthometric Height: e.g. NGVD 29, NAVD 88, Local Tidal
Horizontal
2-D - Latitude and Longitude: e.g. NAD 27, NAD 83 (1986)
Geometric
3-D - Latitude, Longitude and Ellipsoid Height ,
Fixed and Stable(?) - Coordinates seldom change:
e.g. NAD 83 (1993), NAD 83 (2007)
also
4-D - Latitude, Longitude, Ellipsoid Height, Velocities
Coordinates change with time :
e.g. ITRF00, ITRF05
Datum vs. Adjustment
• Datum, NAD83
Metadata
– A set of constants specifying the coordinate system used for
geodetic control… and the set of all points and lines whose
coordinates, lengths, and directions have been determined
by measurement or calculation.
• Adjustment, (1986, 1993, NSRS 2007)
– The process of changing the values of a given set of
quantities so that results calculated using the changed set
will be better than those calculated using the original set.
Definition from the NGS Geodetic Glossary, September 1986
Datum vs. Projection
• Projection, State Plane Coordinate System
– A function relating points on one surface to points on
another surface so that for every point on the first surface
there corresponds exactly one point on the second surface.
A map projection is a special case in requiring that one of
the surfaces be a spheroid and the other be a developable
surface..
Definition from the NGS Geodetic Glossary, September 1986
Metadata
Passive Control
Passive
Control
Active
Control
Continuously Operating Reference Stations (CORS)
> 1,000 CORS sites
~ 200 organizations
OPUS
CORS for monitoring
Tectonic Motion
CORS for monitoring
Vertical Crustal Motion
NSRS
NGS 10-Year Plan
GRAV-D
Ten-Year Milestones (2018)
• NGS will redefine the NSRS vertical datum
based on GNSS and a gravimetric geoid.
– Geopotential Datum
• Height
• NGS will redefine the NSRS horizontal datum,
removing disagreement with the ITRF.
– Geometric Datum
• Latitude, Longitude, Ellipsoid Height
Datum
ellipsoid & geoid
H≈h-N
H = “elevation”
h = Ellipsoidal Height
N = Geoid height
Land
Surface
H h
Ellipsoid
?N
Geoid
model
NAD27, NAD83, ITRF00 (WGS84)
NAD27
ITRF00
NAD83
Earth
Mass
Center
Geoid
Why isn’t NAD 83 good
enough anymore?
NAD 83 vs. ITRF00 (~WGS84)
h83
h00
Earth’s
Surface
ITRF 00 origin
NAD 83 origin
Earth mean radius 6,371,000 meters
NAVD 88
Referenced to Father’s Point
Why isn’t NAVD 88 good
enough anymore?
Approximate level of geoid mismatch
known to exist in the NAVD 88 zero surface:
The Geoid
Geopotential
Surfaces
Ellipsoid
Surface
Standalone Positioning by 2017?
10-15 cm?
1-3 m
• C/A Code on L1
• C/A Code on L2
• New Code on L5
Better resistance
to interference
Faster ambiguity
resolution
Ross Mackay, Kentucky Geodetic Adviser
[email protected]
on the web at
geodesy.noaa.gov
ngs.ky.gov
(502) 564-1474